Mucormycosis, most commonly caused by Rhizopus oryzae, is a life-threatening infection that occurs in patients immunocompromised by diabetic ketoacidosis (DKA), neutropenia, corticosteroid use, increased serum iron and/or severe trauma. Because of the rising prevalence of these risk factors, the incidence of mucormycosis has risen. Despite disfiguring surgery and aggressive antifungal therapy, the mortality of mucormycosis ranges from ~ 50% to 100%. The obvious unmet need for new, effective treatments and preventive strategies has been the driving force of our research program for over seventeen years. We propose to develop a passive vaccine targeting mucormycosis (i.e., an antibody that can be administered to patients with mucormycosis). Data in the academic laboratory of our founder (Dr. Ibrahim) indicate that antibody-based therapy is a promising strategy to treat mucormycosis. This technology is based on the important discovery that the fungal cell surface proteins encoded by CotH facilitate disease progression by allowing R. oryzae to invade mammalian cells via binding to Glucose Regulated Protein 78 (GRP78), a heat shock conserved protein expressed on endothelial cells lining blood vessels during mucormycosis. Importantly, CotH proteins were found to be conserved among Mucorales (organisms that cause mucormycosis) and absent from any other cell type including mammalian. Our data also show that CotH proteins are key determinants of mucormycosis pathogenesis since R. oryzae coth null mutants have markedly reduced virulence in mouse models of mucormycosis. Further, polyclonal antibodies targeting CotH are highly protective against murine mucormycosis caused by R. oryzae, Mucor, Lichtheimia, Cunninghamella, Rhizomucor, and Apophysomyces. Importantly and highly relevant to this application, anti-CotH murine monoclonal antibodies (mAb) raised against a peptide predicted to be present in the binding domain to GRP78, prevent the ability of R. oryzae to invade and injure endothelial cells in vitro and protect mice from mucormycosis caused by several Mucorales to levels that exceed those seen with antifungal therapy. While these mAbs are a promising new therapy for mucormycosis, the feasibility of further clinical development will hinge upon successful humanization of the Abs. Mouse mAbs cannot be used to treat humans, because humans mount an immune reaction to mouse mAbs that can cause rapid removal of the mAbs, systemic inflammation, severe allergic reactions, and even a risk for death. The humanization process prevents these undesirable effects. Thus, we propose two AIMS: 1) Develop our lead murine mAb into a humanized version with retained/enhanced binding ability to CotH proteins; and 2) Determine the protective activity of the humanized Ab in vitro/in vivo and evaluate its toxicity to human tissues. We propose conservative feasibility milestones that are part of a standard, methodical development pathway for our unique mAbs as a novel treatment for mucormycosis. The proposed work will identify a lead humanized Ab that will go into further development to ultimately test in clinical trials as an adjunctive therapy.